docs: def get_common_session_key(self, premaster_secret):
          """K = H(S).
  
          Special implementation for Apple TV.
          """
          k_1 = self.hash(premaster_secret, b'\x00\x00\x00\x00', as_bytes=True)
          k_2 = self.hash(premaster_secret, b'\x00\x00\x00\x01', as_bytes=True)
          return k_1 + k_2